Final answer:
Women were enlisted on a large scale as nurses immediately after the US entered World War I, contributing significantly to the military and medical efforts during the conflict.
Step-by-step explanation:
Immediately after the United States entered World War I, women were enlisted on a large scale into the military and served in various capacities. The most common job title into which women were enlisted was nurses. They played a crucial role in the war effort, serving both on the home front and overseas. In addition to nursing, women took on roles such as driving trucks, repairing airplanes, and performing clerical work to free up men for combat. Those who joined the Women's Airforce Service Pilots (WASPs) contributed by flying planes from factories to military bases. Furthermore, the Naval Reserve Act of 1916 led to nearly 12,000 women enlisting in the US Navy and Marines, holding the unique rank of Yeoman (F), performing clerical tasks, and receiving military pay and benefits. Therefore, the correct answer to the question is A. Nurses.